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Message-ID: <3576aade-d13a-c887-d26b-fd157b82b9a5@arm.com>
Date: Fri, 11 Aug 2023 14:25:31 +0100
From: Robin Murphy <robin.murphy@....com>
To: Zhang Zekun <zhangzekun11@...wei.com>, joro@...tes.org,
will@...nel.org
Cc: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
baolu.lu@...ux.intel.com, robh@...nel.org, nicolinc@...dia.com,
john.g.garry@...cle.com, kevin.tian@...el.com
Subject: Re: [RESEND PATCH 0/2] iommu/iova: optimize the iova rcache
On 2023-08-11 14:02, Zhang Zekun wrote:
> The number of iova_cpu_rcache can grow with the number of cpus in
> iova_rcache, but the size of rcache->depot will not. The deeper of
> rcache->depot can help iova_rcache cache more iovas, and can help
> iova_rcache better dealing with senarios in which drivers allocating
> and free iovas on different cpu cores. We only let the size of rcache->depot
> to grow with the number of cpus which is larger than 32 to avoid potential
> performance decrease on machines which don't have much cpus.
Oh, that reminds me I had started working on this again just before I
was off, only my plan was to get rid of the depot allocation
altogether[1]. However I wanted to finish the second patch on that
branch (to reclaim wasted memory from the depot if the workload changes)
before posting anything - I was feeling really pleased that I'd made it
work until I realised it was leaking all the actual IOVAs... :(
Thanks,
Robin.
[1]
https://gitlab.arm.com/linux-arm/linux-rm/-/commit/2f37ebe93eb282b534bf9e0fd4adc66cfe4b6693
>
> Also, it is unsafe to directly free cpu rcache magazines in free_iova_rcaches,
> add check before freeing it.
>
> Zhang Zekun (2):
> iommu/iova: Add check for cpu_rcache in free_iova_rcaches
> iommu/iova: allocate iova_rcache->depot dynamicly
>
> drivers/iommu/iova.c | 36 +++++++++++++++++++++++++++++++-----
> 1 file changed, 31 insertions(+), 5 deletions(-)
>
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